Abstract
Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter DHT, which can be determined by the present test data. The test results indicated that DHT is not a constant but increases linearly with the temperature variation. A material model was developed for DHT based on the experimental results obtained in this study.
Highlights
Moisture transport plays a main role in predicting the durability and serviceability of cement-based materials
Many researchers consider that the moisture transfer in concrete is driven by a moisture concentration gradient, and the moisture flux is considered as a function of a moisture concentration gradient, and the material parameter associated with the moisture concentration gradient is the coefficient of moisture diffusivity
The effect of the temperature gradient on moisture transfer was treated by using a separating term in the moisture flux equation, and this coupling effect was shown to be significant under non-isothermal conditions [22,23]
Summary
Moisture transport plays a main role in predicting the durability and serviceability of cement-based materials. Temperature fluctuation and moisture changes in concrete structures occur simultaneously; both temperature and the temperature gradient must be considered in terms of moisture transfer. “Soret effect” is a general term to explain the effect of the temperature gradient on diffusing species, such as salt solutions. It was first discussed by the Swiss scientist Charles Soret (1879) [24]. The concentration of salt was higher near the cold end than near the hot end He concluded that a flux of salt was generated by the temperature gradient and the coupling effect was named as “Soret effect”. An available theoretical model was used together with the obtained coupling parameter to compare the model prediction with the present test data
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